Android Open Source - PasswordDroid A E Sprng

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License

The source code is released under:

GNU General Public License

Java Source Code

package de.wuthoehle.passworddroid.crypto;
/*from ww  w. j av a 2s .c  o m*/
/* Copyright (c) 2015 Marco Huenseler <marcoh.huenseler+git@gmail.com>
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

import java.nio.ByteBuffer;
import java.security.GeneralSecurityException;
import java.security.NoSuchAlgorithmException;
import java.security.NoSuchProviderException;
import java.util.LinkedList;
import java.util.Queue;

import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.NoSuchPaddingException;
import javax.crypto.spec.SecretKeySpec;

public class AESprng {
    // This class uses AES-256 in CTR mode to act as a CSPRNG
    // Be sure to know how CTR mode works before using it

    private byte[] nonce;
    private long counter;
    private Cipher generator;
    private Queue<Byte> random_bytes;

    public AESprng(byte[] key, byte[] nonce) throws GeneralSecurityException {
        if (key.length != 32 || nonce.length != 8) {
            throw new IllegalArgumentException("CSPRNG: Need 256bit key and 64bit nonce.");
        }

        this.nonce = nonce;
        this.counter = 0;
        this.random_bytes = new LinkedList<>();

        try {
            // Get AES instance and set 256-bit key
            this.generator = Cipher.getInstance("AES/ECB/NoPadding", "BC");
            this.generator.init(Cipher.ENCRYPT_MODE, new SecretKeySpec(key, "AES"));
        } catch (NoSuchAlgorithmException e) {
            e.printStackTrace();
            throw new GeneralSecurityException("AESprng is unable to operate: NoSuchAlgorithm");
        } catch (NoSuchProviderException e) {
            e.printStackTrace();
            throw new GeneralSecurityException("AESprng is unable to operate: NoSuchProvider");
        } catch (NoSuchPaddingException e) {
            e.printStackTrace();
            throw new GeneralSecurityException("AESprng is unable to operate: NoSuchPadding");
        }
    }

    public static int bitsForRange(int len) {
        return (int) Math.ceil(Math.log(len) / Math.log(2.0));
    }

    public int getInteger(int bits) throws GeneralSecurityException {
        if (bits > Integer.SIZE) {
            throw new IllegalArgumentException("AESprng: Integer can only be " + Integer.SIZE + "bits long");
        }
        byte[] bytes;
        bytes = getRandom((int) Math.ceil((double) bits / 8));

        int result = 0;
        for (int i = 0; i < bytes.length; i++) {
            result |= ((int) bytes[i] & 0xFF) << (Integer.SIZE - ((i + 1) * 8));
        }
        result >>>= Integer.SIZE - bits;

        return result;
    }

    public int getInteger() throws GeneralSecurityException {
        return getInteger(Integer.SIZE);
    }

    public byte[] getRandom(int size) throws GeneralSecurityException {
        byte[] result = new byte[size];

        for (int i = 0; i < size; i++) {
            if (random_bytes.size() == 0) {
                needMoreRandom();
            }
            result[i] = random_bytes.remove();
        }

        return result;
    }

    private void needMoreRandom() throws GeneralSecurityException {
        if (random_bytes.size() == 0) {
            // Plaintext block is now <8 Byte nonce><8 Byte counter>
            // Counter gets incremented after seccessfully producing a ciphertext block
            byte[] plain_block = ByteBuffer.allocate(16).put(this.nonce).putLong(this.counter).array();
            try {
                byte[] cipher_block = this.generator.doFinal(plain_block);
                for (byte i : cipher_block) {
                    this.random_bytes.add(i);
                }
            } catch (IllegalBlockSizeException e) {
                e.printStackTrace();
                throw new GeneralSecurityException("AESprng is unable to operate: IllegalBlockSize");
            } catch (BadPaddingException e) {
                throw new GeneralSecurityException("AESprng is unable to operate: BadPadding");
            }
            counter++;
        }
    }
}

Java Source Code List

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